For those following this meandering hodgepodge of ideas, I have had an interesting development. My past efforts in replicating recipe # 34 in Patent 3,944,425 were failing due to variables that I had inserted into the mix. After taking some time away from this project to work on others, I gathered some dry clay from my backyard diggin's, a second hand cooking pot, a baseball bat, some kitchen sieves, and our old food processor that never gets used anymore. After beating the clay down in the pot, sieving it and running it through the food processor, I was left with a sample of very fine powdered clay with which I set to work making another batch of recipe #34. I combined all the all the dry ingredients and mixed them well. I then mixed in the water. The last step was to add the aluminum sulfate solution and begin mixing with the immersion blender.
Again I was disappointed as the patent states that the mixture should be firm within an hour, but mine wasn't even close, but considering that I wasn't using a verified "Powdered Brick Clay" as the recipe specified, nor was I using the "Lumnite Calcium Aluminate" cement, I decided to wait it out to see if time was a variable that might act in my favor. Despite this shortcoming, the mixture was markedly more liquid than the mixtures I had made with the wet clay slip, which makes me believe that thixotropicity (the propensity for some clays to exhibit gel like characteristics when allowed to sit in a hydrated state" is coming into play here,
On the second day the sample still seemed very soft, but on the third day the sample was firm. I was very hesitant to demold it right away, but opted to chance it. The brick dislodged from the mold very well and felt "leather hard" as those who work with clay might say. I measured the sample for length and weight, and despite having a fire going outside I decided not to attempt firing it right away as I have done with other samples, as I would rather find an opportunity to have it fired in a real kiln at much higher temperatures.
So anyway, to sum things up, by working with dry, powdered clay, I was able to get the cement ratio down to where it should be at approximately 5% of the dry ingredients which I feel is very economical.
Following this experiment, while I allow that brick to dry and await a proper firing, I decided to do another experiment with the wet clay. (I still feel working with wet clay might have it's advantages as you can skip a lot of the labor in processing it.)
I mixed 200 grams of clay slip at 1.51sp with 20 grams of cement, and the other ingredients as a double batch. To this I added about a cup of wet Fuller's Earth. (not the powdered kind, the kind that looks more like kitty litter and is used as an oil/spill absorbent). Being that Fuller's Earth is classified as a refractory material, I felt this would be a good material to use as an aggregate to further stretch the clay foam mixture. Adding the Fuller's Earth effectively quadrupled the volume of the mixture and at 20 grams, gives me the same economy as the brick made with the dry clay. Fuller's Earth is about $10 for a 40 lb. bag. This batch just happened to be enough to fill all four cavities in my mold, so now I wait.
I would be interested to hear from anyone who would be willing to let one of my experimental bricks "reside" in your batch box over the next heating season. I am interested to discover how the material survives over time in an environment that is much hotter than the one my fireplace can provide. The bricks are only about 1"x1"x 3.75" so they wouldn't take up much space.